November 25, 1892.] 



SCIENCE. 



299 



As it happened, we had in stock a number of paste-board boxes 

 some 93 millimeters wide, 143 millimeters long, and 48 millimeters 

 deep, all inside measurements. The dimensions of our standard 

 slide are 48 x 28 millimeters. By means of two wooden parti- 

 tions, some 3 millimeters thick, running lengthwise, each box was 

 divided into three equal compartments, the partitions being held 

 in place by glue reinforced by two small tacks at each end. 

 Heavy Manilla wrapping paper, such as we also had in stock, was 

 ^hen cut into strips 25 millimeters wide and as long as the sheet 

 of paper would allow, in this case about 7 feet. These strips 

 "were then bent into a series of folds, as shown in the accompany- 

 ing illustration, the apices being rounded, not pinched flat. If 

 carefully done, the folds when crowded gently together act as a 

 spring. Two of these folded strips were then placed lengthwise 

 in each compartment, and the slides introduced, standing on end, 

 between the folds at the top. A box as thus prepared readily 

 iholds three rows of 50 slides in a row, or 150 altogether. 



Each sUde is separated from its neighbor in the same row by a 

 double thickness of Manilla paper, which, owing to its manner of 

 folding, acts as a spring, and avoids all possible danger of break- 

 age. When all the compartments are filled, the space between 

 the tops of the slides in any row is but about 3 millimeters ; but 

 there is, nevertheless, no difficulty in removing a slide or in 

 getting at it to read the label without removal, since, owing to 

 the yielding nature of the paper, the tops may be readily drawn 

 apart. In this respect the box offers a great advantage over 



those with rigid wooden compartments, such as are commonly 

 in use. The first box was made merely as an experiment. It 

 proved so satisfactory that, for the time being at least, it is the 

 form adopted for storing the several thousand slides forming the 

 museum collections. 



I have attempted to show the arrangement as above described 

 in the accompanying drawing. In reality the slides are held 

 much more firmly than indicated, since the paper bulges and 

 •comes against both the front and back of the slides, the full 

 length of the fold, instead of merely at the bottom. It will very 

 likely strike the reader that a better material than paper might 

 be found. I can only state that after considerable experimenting 

 the paper was, all things considered, found most satisfactory. 



Bepartment oJ Geology, TJ. S. National Museum, Washington, B.C. 



SPONTANEOUS COMBUSTION IN MINES.' 



BY PROFESSOR ARNOLD LTTPTON, YORKSHIRE COLLEGE, LEEDS, 

 ENGLAND. 



The lecturer remarked that most of the difficulties of a mine 

 «ould be overcome in certain well-known ways : water could 

 be raised by pumping-engines; gas carried away by ventilation, 

 tind the danger obviated by safety lamps; but spontaneous com- 

 bustion, in some cases, could not be prevented, and, when once 

 begun, could not always be stopped, except by filling the pit with 

 water. 



' Summary of a lecture on the loth of October last, at the Philosophical 

 Sail, Leeds. 



Spontaneous ignition of coal was well known to ship-owners 

 and insurance companies, large cargoes of coal being especially 

 liable to take fire upon long journeys. In the same way, a great 

 heap of coal on the surface was liable to take fire, especially if it 

 was small coal or slack. For that reason it was necessary in 

 storing slack not to have the heaps too wide or deep. A heap ten 

 feet deep might not fire, while a heap twenty feet deep of the 

 same coal would be very liable to fire. A small heap of slack 

 laid against the outside of a boiler-flue or steam-pipe would proba- 

 bly take fire in a short time. Heaps of slack and broken coal 

 left in the mine were very liable to take fire, and much smaller 

 quantities would fire in the mine than on the surface, because 

 it was warmer underground, and the superincumbent strata 

 upon the slack and broken coal prevent the heat from es- 

 caping. Spontaneous ignition was very frequent in the thick 

 coal-miles of South Staffordshire, Warwickshire, and Leicester- 

 shire, and it was necessary that these pits should be watched 

 every hour of the day and nigbt lest a fire, having broken out, 

 should obtain the mastery before it was discovered. If a fire was 

 detected whilst yet smouldering, the heated material is dug out 

 if possible and the place filled with sand. Sometimes the fire was 

 extinguished by pumping water onto it. In some mines water 

 was laid on at a high pressure for the purpose of throwing jets of 

 water onto any fire that may occur. It was usual, however, in 

 mines liable to spontaneous combustion, to separate the district 

 containing the waste heaps of slack or broken coal from the rest 

 of tlie mine by means of walls or dams of brick and clay and 

 sand, so that the smouldering fire, producing carbonic acid gas, 

 extinguishes itself by its own smoke. Sometimes an apparently 

 solid mass of coal took fire. In this case the apparently solid coal 

 has been cracked and crushed, and air has been able to enter into 

 the cracks to support combustion. In mines liable to this species 

 of accident, the manager has a very anxious time, and his deputies 

 must unceasingly patrol the pit. Sometimes it was impossible to 

 isolate a fire, owing to air drawing through cracks in the pillars 

 of coal surrounding the fire, and the men were beaten back by 

 the flames, and had to abandon the mine. The shafts were then 

 partially filled and covered so as to exclude the air, and in the 

 course of three or four months it generally happened that the fire 

 was extinguished. 



The cause of these fires was perhaps not entirely explained. 

 It used to be supposed that the decomposition of the sulphuret of 

 iron, called iron pyrite.^, produced heat sufficient. This idea was, 

 however, now abandoned by the leading chemists who had studied 

 the question. Sir Frederick Abel and Dr. Percy, in a report to 

 the Royal Commission in 1875 on the "Spontaneous Combustion 

 of Coal in Ships," suggested the decomposition of the coal as the 

 probable cause. Professor Vivian B. Lewes, in 1892, contributed 

 a paper to the Society of Arts, in which he stated, as the result of 

 the work of Richters and himself, that newly-cut coal would 

 absorb oxygen to the extent, in some cases, of three times its own 

 volume. This oxygen produced a kind of slow combustion, and, 

 where the heat could not escape, the temperature of the mine was 

 raised to that of 800° to 900° F., and at this temperature, if there 

 was any air near to the coal, it would take fire. 



There were only two ways, apparently, of preventing this spon- 

 taneous combustion. One was to cool the heap by ventilation. 

 But the ventilation to be efficient must be equal to that of a coal- 

 heap on the surface, and it was known that a heap of small coal 

 twenty feet thick and thirty or forty feet wide was very liable to 

 take fire; therefore, if the heap of coal in a mine was to be cooled 

 •by ventilation, the ventilating roads would have to be not much 

 more than fifteen feet apart, and a cool current of air through 

 each. This, as a general rule, was impracticable; and therefore, 

 as.a general rule, the prevention of spontaneous ignition by ven- 

 tilation was impracticable. The other method was to exclude the 

 air from the mass of coal that was liable to tire by means of walls 

 of soft clay or by walls of brick and mortar and sand, or solid 

 pillars of coal. The portion of the mine so walled off might get 

 very hot, raising the temperature of the mine ten or twenty de- 

 grees above the normal temperature of the earth ; but it could not 

 take fire if the air was excluded. 



